NIOSH respirator protection factors

NIOSH lists protection factors for different types of respirators. Table 20 gives protection factors to be noted in the use of respirators. It should be noted that this table is based on Mine Safety and Health Administration guidelines. 

Assigned protection factor (APF) The minimum level of respiratory protection that a respirator can be expected to provide, assuming it is properly fitted, worn, and functioning. APFs are assigned by NIOSH. 

Assigned protection factor—A rating assigned to a respirator style by OSHA or NIOSH this rating indicates the level of protection most workers can expect from the properly worn, maintained, and fitted respirator used under actual workplace conditions. 

Protection factors are important criteria for selecting respiratory protective equipment. The protection factor must be sufficiently high to reduce the contaminant inside the facepiece to an acceptable level, usually taken as the TLV, or threshold limit value. The Appendix lists the TLV values for commonly spilled materials. These data are used in the following manner (ACGIH, 1999 NIOSH, 1994). A spill of a substance with a TLV of 5 ppm, which according to calculations could rise as high as 5,000 ppm, would require a respirator with a protection factor of at least 1,000. For a safety factor of 2, a protection factor of 2,000 would be required. Pressure-demand SCBAs, which have a protection factor of about 10,000, represent the ultimate in safety and are generally used at spill scenes because the exact substance and the level of the contaminants are not known for certain until measurements have been made. 

Because each worker s environment is different, and the amount of occupational exposure to crystalline silica dust varies, an occupational exposure determination should be completed before selecting an appropriate respirator. The minimum respiratory protection for a worker who is working with crystalline silica dust, but is not doing abrasive-blasting, may be an N95 NIOSH-approved respirator. However, the exposure to crystalline silica must not exceed the assigned protection factor of the respirator. 

RSL is a decision-making tool developed by NIOSH to help employers choose the right kind of respirators for their workplaces by taking them through a series of questions on how and in what environments the respirator will be used, and with what types of contaminants. The RSL takes into account the Assigned Protection Factors (APF) developed by OSHA to indicate the level of protection that a respirator or a class of respirators is expected to provide. 

This data contains existing values of concentrations that are immediately dangerous to life or health, IDLH. The data are provided by National Institute for Occupational Safety and Health, NIOSH, to help in selection of appropriate respirators. Two factors were considered when establishing the IDLH limits (a) workers must be able to escape such an environment without suffering permanent health damage, (b) workers must be able to escape without severe eye or respiratory tract irritation or other conditions that might impair their escape. The current definition has no exposure duration associated with it. Workers should not be in an IDLH environment for any length of time unless they are equipped and protected to be in that environment. IDLH values were determined based on animal and human data. 

The company is to evaluate the respiratory hazard(s) in each workplace, identily relevant workplace and user factors, and base respirator selection on these fectors. Included are estimates of employee exposures to respiratory hazard(s) and an identification of the contaminant s chemical state and physical form. This selection included appropriate protective respirators for use in IDLH atmospheres, and limits the selection and use of air-purifying respirators (APR). All selected respirators are to be NIOSH-certified. 

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